It is known to provide an inflator for inflating an inflatable vehicle occupant protection device. One particular type of inflator uses a solid propellant to generate inflation fluid. The solid propellant, when ignited, produces inflation fluid for inflating the protection device. Upon actuation, the inflation fluid is discharged from the inflator through an inflation fluid outlet, and the inflation fluid is directed into the protection device.
Solid propellant inflators can be two-stage inflators in which two separate stages are individually actuatable to produce inflation fluid. A first or primary stage is configured as a primary source of inflation fluid. A second or secondary stage is configured as a secondary source of inflation that can supplement the primary stage. The primary stage can be actuatable any time a vehicle collision sensor determines a collision of a predetermined severity. The secondary stage can be selectively actuatable depending on sensed vehicle and/or occupant conditions, such as a seat position, seatbelt buckle latched/unlatched condition, sensed seat weight, and collision severity. When actuated, the secondary stage supplements the inflation fluid delivered to the protection device by the primary stage.
Two-stage inflators can include a housing with a primary chamber containing a primary propellant and a secondary chamber containing a secondary propellant. The primary and secondary propellants are ignitable via respective primary and secondary ignitors, which are operatively connected to a controller that determines whether to actuate the primary stage alone, or the primary and secondary stages together.
The primary and secondary chambers can be connected to a discharge chamber through which the inflation fluid generated by the primary and/or secondary stages is discharged to the protection device. To prevent the ignition of the primary stage from unintentionally igniting the secondary stage due to hot particles passing through the discharge chamber, blocking means, such as a wall or membrane, can be used to divide the discharge chamber into separate portions associated with the primary and secondary stages, respectively. This configuration, however, can complicate construction of the inflator by introducing additional manufacturing steps and requiring the addition of components, such as particulate filters.